1. Field of the Invention
The present disclosure relates to image forming apparatuses using an electrophotographic method or an electrostatic recording method, such as copying machines, printers, and faxes.
2. Description of the Related Art
For example, in an image forming apparatus that forms a toner image on an intermediate transfer belt serving as an image carrier and transfers it onto a recording material, a cleaning unit is provided for removing untransferred toner that is not transferred onto a recording material and remains on the intermediate transfer belt. A rubber cleaning blade, for example, is widely employed as the cleaning unit. If an excessive frictional force acts between the cleaning blade and the image carrier in such an image forming apparatus, the edge of the cleaning blade curls up, which may possibly cause a cleaning defect. The untransferred toner also plays the role of a lubricant for reducing the frictional force between the cleaning blade and the image carrier. However, the frictional force cannot be sufficiently suppressed only with untransferred toner in some cases, and toner is mandatorily supplied to the cleaning unit after printing and before next printing is started. Japanese Patent Laid-Open No. 2002-323803 discloses mandatorily supplying toner to a cleaning blade using a cartridge used in image formation.
Possible exemplary methods for supplying toner to the cleaning blade include a method of temporarily suspending printing every time a predetermined number of sheets are printed and supplying a large amount of toner at that time, and a method of supplying a small amount of toner every time one sheet is printed. However, with the former method, printing is periodically suspended for a long time, and once a toner supply operation starts while several print jobs are being successively performed, a user needs to wait for a long time until printing ends, for example. On the other hand, with the latter method, the toner supply operation is performed every time a recording material is printed, and consequently, throughput during successive printing will decrease. In particular, mass printing is often performed in a monochrome mode in which one color is used for printing, and is significantly affected by reduction in usability due to the toner supply operation.